The present invention pertains generally to devices for coupling a lift cable or hook to a heavy article to be lifted such as metal plate.
A problem exists in handling steel plate as the same must be modified to accept a lifting instrumentality and when so modified the plates are not stackable by reason of an irregular surface.
A proposed solution is disclosed in U.S. Pat. No. 4,304,432 issued to one of the present inventors which patent discloses, inter alia, a three-piece device having a pair of lift elements and a central locking element. A flexible member yieldably connects the three pieces and permits displacement of same during attachment to an undercut opening on a metal plate. The patented device described is not in wide use in the construction trades for one reason or another. Such devices are subjected to very hard use in the field and must withstand extremely rough treatment.
U.S. Pat. No. 2,563,164 discloses a lifting attachment with dovetailed members spaced by a centrally disposed key member all joined by a pin.